1. Field of the Invention
The invention relates to a contact arrangement for a pressurized gas circuit breaker wherein the contact arrangement comprises: a first tubular contact member and a second contact member axially arranged therewith, an arc being drawn between said contact members and blasted by pressurized gas when the breaker is interrupted under load; a nozzle body arranged at the end face of the first contact member; and a hollow cylindrical means of ferromagnetic material arranged within the first contact member.
2. Description of the Prior Art
The interrupting capacity of a high-voltage power circuit breaker under conditions of a terminal short circuit and a remote short circuit can be made larger by increasing the resistance of the arc channel in the immediate time-wise vicinity of the current zero crossing. There are essentially two ways to increase this resistance. The first way is to intensively cool the arc. In air-blast breakers, the arc is cooled by the pressurized gas stream released during the interrupting process. In this process, the conducting cross section of the arc is reduced or the resistance per unit of length of the arc is increased.
The second way to increase the resistance of the arc channel is to lengthen the arc itself. Such a lengthening of the arc depends largely on the contact arrangement. It can be achieved for example, by the use of tubular contacts having hollow nozzle-shaped bodies at their end faces wherein the arc bases (burn spots) are driven into the nozzles under the influence of the gas stream. This effect brought about by the use of tubular contacts and nozzle-shaped bodies can be further enhanced by additionally arranging a hollow cylindrical means of ferromagnetic material within the interior of the tubular members. These cylindrical means can be designed so that an electromagnetic force drives the arc bases further into the nozzles, thereby additionally lengthening the arc.
However, in the latter type arrangement, when an arc is driven into the interior of the hollow nozzles by the electromagnetic force, restriking of the arc can occur. Such restriking can reestablish the arc bases on the rim of the nozzles, thereby adversely affecting the initiated quenching process.
It is an object of the present invention to provide a contact arrangement for a pressurized-gas circuit breaker of the above described type wherein restriking of the arc is prevented and, thereby increasing the interrupting capacity of the breaker.